For the purpose of this invention we may consider two types of optical imaging systems: planar and non-planar electronic systems. There are many advantages to using non-planar image sensor arrays including wide field of view, low aberrations and reduced complexity of the systems. However, the majority of available optical imaging systems used today are planar due to restrictions imposed by current techniques used for fabricating optoelectronic systems. Existing technologies are to a large extent geared toward the production of rigid devices on flat surfaces. The resulting systems do not have the ability to absorb strains as required for non-planar designs.
In order to achieve non-planar optoelectronic systems one may process devices directly onto curved surfaces or alternatively onto flat surfaces which are then deformed into the desired shape. Both methods have been actively researched in the past decade with varying degrees of success.
Alternative routes to creating curved focal plane arrays include template generation by ion beam proximity lithography and relief transfer by step and flash imprint lithography; large-scale, heterogeneous integration of nanowire arrays by contact printing; and soft lithographic printing of amorphous silicon on curved substrates. The above-mentioned techniques suffer from limitations with multilevel registration of circuit layers and use of low performance materials which struggle to compete with single crystalline silicon devices currently in use.
Other relevant methods include wet chemical thinning of silicon wafers to produce curved silicon substrates for subsequent processing; and micro-structuring of monolithic silicon die using a deep reactive ion etch on SOI wafers. The prior is not compatible with current semiconductor fabrication processes and the latter is undeveloped due to the plethora of manufacturing challenges. Therefore a need exists for viable routes for production of curved imaging arrays with the utilization of conventional planar processing technology and subsequent deformation to produce different shapes of imaging arrays.